• Rate of anastomotic leakage [ Time Frame: 90 days after surgery ]
  detected by imaging techiques (CT scan or MRI)
• Rate of surgical site infection [ Time Frame: 90 days after surgery ]
  1)superficial and deep infection:clinical observation of purulent discharge from the wound and/or bacterial staining from the wound 2)organ or deep space infection: imaging techniques (CT, MRI, USS)
• Rate of prolonged postoperative ileuss [ Time Frame: 90 days after surgery ]
  detected by clinical observation of the first bowel movement after the surgery

• microbiome composition [ Time Frame: 3 months after study start date ]
  The composition of luminal microbiome and mucosal-associated microbiome will be studied by DNA analyses from fresh fecal samples and surgical anastomosis material, accordingly
• microbiome composition [ Time Frame: 6 months after study start date ]
  The composition of luminal microbiome and mucosal-associated microbiome will be studied by DNA analyses from fresh fecal samples and surgical anastomosis material, accordingly
• impact of microbiome composition on length of hospitalization [ Time Frame: at the time of patient's discharge of the hospital ]
  length of hospitalization will be detected and analyzed in association with microbiome composition
• Correlation between detected bacterial OTUs (Operation Taxonomic Units) and the event of reintervention [ Time Frame: 90 days after surgery ]
  In the patient group with the event of reintervention, an abundance of specific OTUs will be analysed in compare with patients with no event of reintervention.
• impact of microbiome metabolites on intestinal epithelial cell proliferation and wound healing [ Time Frame: 6 months after study start date ]
  Monolayers of human colon cancer cell lines HT29 will be incubated for 24 hours with fecal water from patients with surgical complications and matched control patients without complications. Proliferation will be calculated in two manners: 1) The time of the closure of the scratch defect will be evaluated and compared in the two group., 2)Proliferation rate will be analyzed by immunohistochemistry marker Ki 67, expression of Ki 67 will be evaluated in cells at the borders of the scratch defect
• Expression intensity in cytoplasm of protein ligase HACE1 in tumoral and non-tumoral tissues [ Time Frame: 6 months after study start date ]
  Immunohistochemistry with anti-HACE1 antibodies will be used to detect expression levels in tumoral (colorectal cancer) and non-tumoral (anastomotic sample) tissues. In a case of decreased expression, tissues will be analyzed by methylation PCR to detect an aberrant methylation of HACE1 and its hypermethylation
• Expression intensity in cytoplasm of protein ligase HACE1 in tumoral and non-tumoral tissues [ Time Frame: 3 months after study start date ]
  Immunohistochemistry with anti-HACE1 antibodies will be used to detect expression levels in tumoral (colorectal cancer) and non-tumoral (anastomotic sample) tissues. In a case of decreased expression, tissues will be analyzed by methylation PCR to detect an aberrant methylation of HACE1 and its hypermethylation

Intro: Recent studies on colorectal cancer surgery have been focusing on the role of intestinal microbiome on surgical outcomes. Standard perioperative cares, like mechanic bowel preparation (MBP), administration of antibiotics (ABT) and surgery-related stress and injury influence the microbiome composition and possibly induce a shift toward a microbiome dysbiotic state, which predisposes to complicated postoperative course. Microbiome composition changes and enhanced virulence factors may increase the risk of postoperative complications, such as anastomotic leakage (AL), surgical site infection (SSI), and postoperative ileus (PI), which are known to impact on patient's overall survival and cancer recurrence.

Objective: The primary objective is to investigate if a significant association might exist between the microbiome composition and the occurrence of postoperative complications at 90 days.

Methods: 3 different microbiome samples will be taken from all patients. Two fresh fecal samples for detection of LM and fecal water preparation: a) a day before the surgery before MBP and/or ABT (LM1), b) postoperatively after first bowel movement (LM2). One sample will be taken intra-operatively from the stapled resection lines of circular stapler used for forming a colorectal anastomosis, to detect the MAM and to perform immunohistochemistry staining for detection of HACE1 expression.

DNA analysis will be performed for all samples. IHC will be performed for detecting HACE1 expression in the tumor and colorectal anastomosis tissues using anti-HACE1 antibodies. .

For proliferation assessment, human colon carcinoma cell lines HT29 will be plated in monolayers and scratched with a single scratch. Monolayers will be incubated for 24 hours with fecal water from patients with surgical complications and matched control patients without complications.

Descriptive statistics will be performed to describe the study population. This project aim to describe microbiome composition and its impact on postoperative complications.

• Adenocarcinoma of the Colon
• Adenocarcinoma of the Rectum

Inclusion Criteria:

• Adult ≥ 18 years old
• With histologically confirmed rectal or left colon adenocarcinoma by biopsy material from colonoscopy
• Having elective colorectal surgery after standardized bowel preparation
• Affiliated to a social security system
• Signature of informed consent

Exclusion Criteria:

• Major surgery 30 days before scheduled colorectal surgery
• Administration of systemic antibiotic therapy within 30 days prior to planned colorectal surgery
• Presenting a contraindication to elective colorectal surgery
• Patient protected by law
• Pregnant or breastfeeding woman